The von Hippel-Lindau (VHL) tumor suppressor gene plays a critical role in the pathogenesis of clear-cell renal carcinoma and CNS hemangioblastomas. The functional role of the VHL gene in cell growth, cell differentiation, kidney and brain development is not well understood. VHL-deficient mice generated by conventional gene targeting in embryonic stem (ES) cells die in utero at 10.5 to 12.5 days of gestation and therefore can not provide the mouse model needed for the analysis of the developmental and long term effects of VHL deficiency in kidney and brain. In this project a conditional gene targeting strategy based on the Cre/loxP system will be used to generate mice in which a temporally controlled and tissue-specific inactivation of VHL can be accomplished. Such a mouse model will permit the study of VHL function in specific tissues at specific times of development. The work described will be performed in the outstanding environment of the Whitehead Institute for Biomedical Research in the laboratory of Dr. Rudolf Jaenisch, a world-renowned expert in the field of mouse developmental biology and pioneer in transgenic and gene targeting technology. Collaborators include Dr. Vikas Sukhatme, Renal Division Chief at Beth Israel Deaconess Medical Center, who will provide reagents and technical expertise for the analysis of VHL-deficient mice in the later stages of the project, as well as Dr. Helmut G. Rennke, Associate Professor of Pathology at Brigham and Women's Hospital and internationally renowned expert in renal pathology who will help with histological analysis of VHL deficient mice. The PI is currently a second year renal fellow at Beth Israel Deaconess Medical Center and trainee in Dr. Jaenisch's laboratory as an integral part of his renal fellowship. He has three years of experience in basic molecular biology methods from his work as a Research Fellow at Massachusetts General Hospital. The new methodologies the applicant will learn include all aspects of cutting edge gene knockout technology, such as targeting vector design, genetic manipulations of ES cells in culture, genetic recombination mediated by Cre/loxP, and generation of mice by blastocyst injection, furthermore he will learn in situ-hybridization and advanced PCR techniques. He is absolutely committed to a career centered on basic research in an academic Nephrology division applying the techniques learned during the award period.